Over on Grokdotcom, there's an excellent article about The Search Engine's Love Affair with Blogs by Juan Tornoe. As Tornoe points out, and we've said many times ourselves, "search engines love blogs." And Tornoe goes on to say, it's not as simple as it sounds:
First, there's the issue of relevance. A blog won’t magically give you a top ranking position on Google, Yahoo! or the like. The content your blog has, the frequency with which such content is being updated, and the amount of relevant incoming links to your site are some of the factors that will make-or-break the effectiveness of your weblog.
Don’t add a blog to your site if you're not willing to consistently invest time and effort. An outdated blog will reflect the opposite image of whatever it is you want potential customers to know about your company.
That second paragraph (the emphasis is mine) is key. When we speak to prospects looking to add a blog to their marketing mix, we emphasize this point along with the following point that a blog that's not consistently update has the same effect as a storefront with broken windows and no inventory. It's not good for your business image.
It bears repeating that a business blog is a marketing tool and like any other tactic you use to market your business, it must be done consistently and professionally to get the results you want.
Juan Tornoe's article is excellent so do read it when you get a chance.